The field of the invention relates to rubber laminated bearings used to support and seal a limited-movement shaft that penetrates the wall of a pressure vessel.
In the prior art, rubber-laminated bearings as disclosed in U.S. Pat. No. 2,900,182, include multiple alternate laminations of metal (or other strong inextensible material) and rubber (or generally any elastomer) bonded together, the rubber layers in particular being thin relative to their width and/or of relatively stiff composition. Lateral motions between succeeding metal laminations are permitted by shearing action within and parallel to the intervening rubber laminations, while the stack of laminations so-formed can often sustain very high normal forces (eg, 20,000 psi or more) with very slight compression because of negligible extrusion of rubber out from between the metal laminations. They can be made with laminations in any shape, with apertures or not, and with various cross-sectional configurations, including truncated planar, conical, spherical, chevron-shaped or cylindrical layers. Often, to provide complete practical bearings, thicker layers of metal are bonded on the outsides to the underlying laminates as described, forming external layers that are load faces. These two outer layers may be shaped to conform with and to seal with respect to mating members and to provide for keying to the latter for orientation and prevention of slipping.
When the external load faces of such a bearing are interposed between complementally-contoured and opposed loading members, it can resist thrust, radial or combined forces normal to its layers, depending upon its configuration. Relative lateral movement between the opposed loading members, which may include pivoting about a normal axis as well as transverse or lateral shifting, results in a distribution of the aforesaid shearing movements between individual rubber layers. These relative motions are accompanied by opposing forces proportional to their extent, caused by shear stress in the rubber laminations.
An additional property of such a load-bearing laminate stack that contains one or more apertures is the capability of sealing the space occupied by the laminations between the opposing members against the lateral or transverse flow of fluids, ie, liquids or gases, between the periphery of the laminate stack and an aperture, and making them essentially impervious even under substantial differential pressure. This is shown in U.S. Pat. Nos. 3,532,174 and 3,610,347, where such bearings for a vibratory drill mechanism were sealed against drilling fluid and were indicated to be of cylindrical (ie, radially loaded) or acute-angled conical (combined loading) configurations. U.S. Pat. Nos. 3,734,546, 4,068,864, 4,068,868, 4,076,284 and others typically show spherically-configured rubber laminate bearings used to seal the joints of submerged oilfield pipe sections while permitting flexibility between them. Further, U.S. Pat. Nos. 3,504,902/3/4 show spherical rubber laminated bearings used in the throat of rocket nozzles to permit control of the thrust vector by tilting the nozzle, while sealing against the lateral escape of the hot gasses.
None of these laminated bearing references were found to provide for sealing a shaft that penetrates the wall of a pressure vessel so that motions applied on one side may be carried to the other to accomplish some purpose. Indeed, all of the patents cited in the previous paragraph are functionally dependent upon a free path for fluid flow through the pipe or nozzle that is surrounded by the bearing-seal that is employed. If their pipe or channel for fluid flow were to be considered a shaft with a longitudinal hole through it, that hole would completely invalidate the present purpose, which involves preventing any such flow from one side to the other of the wall through which the shaft passes.
Existing methods of providing the desired sealing function for a shaft penetrating the wall of a pressure vessel employ a lip seal or face seal, conventional though designed for high pressure, that slides on the surface of the shaft or on a flanged part of it. All such methods must contend with friction torque, all the greater under conditions of extreme pressure even when anti-friction materials such as reinforced tetrafluoroethylene are used. Moreover, because sliding on a surface is involved, its smoothness must be assured and care must be taken to prevent ingress of foreign material or objects that could not only cause rapid wear but could damage the sealing integrity of the seal or shaft surfaces.
In this invention, one of the loading members is an enlarged contoured enlargement or flange at the midsection of a shaft, ie, between its ends, against one or both sides of which enlargement or flange there is seated a complementally-contoured or conforming rubber-laminated bearing-seal having an aperture as described. The shaft extends through a bearing aperture and on through an aperture in a bearing housing or receptacle part of the wall of a pressure vessel. This housing or receptacle comprises a radially inward load-supporting seat or appropriately contoured annular flange against which said bearing-seal is seated, ie, the other loading member of said bearing-seal is part of or connected to the wall. The wall separates two liquid, gaseous or even vacuous media, all considered as fluids herein. The nested laminations or layers of said bearing-seal may be surfaces of revolution about an axis that corresponds to the shaft axis. Hence, the shaft can carry limited movements, rotational or lateral and parallel to the laminations, from one side to the other of the wall while being sealed against any fluid flow between the sides despite substantial pressure differences, and while resisting the resulting thrust. The force or torque reaction is negligible due to friction and small with small movement compared with the relatively high friction of conventional sealing methods.
The reasons for penetrating the wall of a pressure vessel with a sealed movable shaft generally dictate that some functional mechanism be provided at each end of the shaft, coupled with it to impart or receive torque or force and motion to it. Thus, one potential use is in the intense hydrostatic pressure environment of undersea applications at great depths, carrying limited or oscillatory motion through the hull of a manned or robotic submarine craft. Failure to provide the expected sealing effect could be catastrophic. Backup using a second laminated bearing-seal or conventional O-ring seals or their functional equivalent in series can be used for protection against such events.
It is an object of the invention to provide a new means with very low friction and reliable long life for sealing a limited motion shaft that penetrates the wall of a pressure vessel to accomplish some purpose.